1. Technical Field
The present invention relates generally to a method for parameterizing a geographical area. More particularly, the present invention is directed to a method for calculating rectangular parameterization of an arbitrarily shaped geographic area for use by a satellite based communication system.
2. Discussion
The overall control system portion of cellular, satellite, or other radio telecommunication networks often tracks the locations of the mobile subscriber units for which communication services are to be provided. The system activates a ring signal to alert a particular mobile unit to an incoming call. System resources can be conserved by activating the ring signal in only the illumination area where the mobile unit is located. In particular, the overall power consumed by the system in transmitting a ring signal is reduced when the ring signal is activated in fewer cells or geolocations. This power consumption problem becomes particularly important in a satellite-based network where one satellite may cover a very large geographic region. In addition, the number of incoming call or page alert messages that can be delivered using a given ring signal delivery capacity is increased when each ring signal is activated in fewer cells or geolocations.
Accordingly, the telecommunication network benefits from maintaining current, accurate and precise geolocation data for each mobile unit to which communication services are being provided. This type of geolocation data thus allows the system to more efficiently focus the ring signal coverage on a minimum area. With this type of geolocation data, the system can achieve the maximum conservation of system power and ring signal capacity resources while still achieving a good probability that the narrowly focused ring signal would be received by its intended mobile unit. This type of geolocation data also allows for increased billing accuracy, enhanced 911 and other emergency type services, as well as navigation type services via the telecommunications network.
However, in present satellite-based networks other system resources are consumed for maintaining current, accurate and precise location data for each mobile unit. In particular, an undesirably large amount of overhead communications is required for tracking the location of each mobile unit. To maintain current location data, the system might engage in a communication session with a mobile unit each time a mobile unit moves a small distance from the last location recorded by the system. Unfortunately, for a given amount of spectrum allocated to the network, these overhead communication sessions would prevent the network from conveying a corresponding amount of subscriber traffic. In other words, the network benefits from minimizing the number of such overhead communication sessions because minimizing overhead communication sessions maximizes the system capacity available for conveying subscriber traffic. But, minimizing the number of overhead communication sessions reduces the system""s ability to accurately and precisely track mobile unit locations.
Accordingly, network resources are optimally conserved by balancing ring signal illumination area against overhead traffic communication volume. Unfortunately, conventional radio telecommunication networks strike a very crude balance between illumination area and overhead traffic communication volume. As a consequence, power consumption is undesirably high in many situations, and an undesirably high proportion of the allocated spectrum is used for overhead communication sessions in other situations.
In particular, conventional mobile units register with their system in accordance with a temporal re-registration schedule. Using a temporal schedule, slow moving mobile units waste precious overhead traffic capacity by informing the system of mobile unit locations that are little changed from previous locations. Conversely, a frequent call-in schedule must be adopted to accommodate fast moving mobile units, or else the fast moving mobile units are likely to move so far from known locations that ring signals activated in a limited area will not be received.
Other know types of mobile units register with their systems when they move out of a predetermined area. This technique improves upon temporal re-registration, but still fails to adequately compensate for differences between various types of mobile unit equipment and mobile unit users. For example, an optimum balance of illumination area against overhead traffic communications for faster moving mobile units is likely to differ from an optimum balance for slower moving or stationary mobile units. When a single illumination area is used for all proximately located mobile units, the illumination area is likely to be undesirably large for slower mobile units and undesirably small for faster moving mobile units. Thus, too much power is consumed is ringing slower mobile units and too much overhead traffic communication is required to track faster moving mobile units.
Moreover, conventional prior art networks fail to adequately consider different user needs in configuring ring signals. For communication services to meet user expectations, all mobile units need to have a good probability of receiving ring signals activated in the areas where they reside. While this good probability of receiving a ring signal is adequate for most users, certain VIP users and emergency service providers may need a higher probability of receiving their ring signals. The power consumption and equipment costs associated with improving this good probability to an excellent probability for all users are disproportionately high. Thus, conventional networks force all mobile unit users, including those involved in providing emergency services and VIP users, to experience the same good probability of receiving incoming calls as is provided for all other users.
In view of the above it is desirable to provide a method for reducing the amount of overhead required for geolocating a mobile unit. It is further desirable to provide a method for calculating and assigning location area codes for a predetermined geographic area. Finally it is desirable to provide a technique and method for efficiently optimizing the partitioning of a geographic area into sub-partitions.